chapter  15
26 Pages

Impacts and Extinctions

Cloud was referring to the birth of our planet about 4.6 billion years ago, but we can look much further back, some 14 billion years ago, to when the universe was created in an unimaginably large explosion known as the “Big Bang.” This explosion produced the atomic particles that later formed galaxies, stars, and planets ( Figure 15.2 ). The fi rst stars probably date to about 1 billion years after the Big Bang, and stars continue to form today.